A growing body of evidence indicates that an ocean is hidden
beneath the icy crust of Jupiter's second moon, Europa.
Galileo mission data reveal surface features indicating
surface disruption, magnetic fields indicating moving,
conducting fluids, and cycloidal cracks likely caused by
ocean tides. Spectral evidence from the NIMS indicates
hydrated materials, suggested to be salts, on the surface in
concentrated deposits closely associated with the fractures
and disturbed terrain [McCord et al., 1998, 1999]. Hydrated
salts are indicated also by thermal evolution models of
Europa's interior and laboratory studies of meteorites
[Fanale et al., 1977, 1998; Kargel, 1991]. The hydrated
mineral deposits might result from exposing salty ocean
water to the surface. To investigate this possibility we
prepared frozen sulfate and carbonate brine samples by rapid
thermal quenching and measured IR reflectance spectra of
these flash frozen brines as a function of hydration level
in situ in cold vacuum. Ab intio calculations of
intermolecular distances, molecular mechanics simulations of
aqueous salt solutions, and the temperature and cooling rate
in our experiment indicate the anions should be fully
solvated and the average number and configuration of
hydration waters in the first solvation shell should be
``frozen in" during deposition. Thus, we should be dealing
with frozen brines rather than crystallized minerals. These
spectra are even more like the Europa non-ice endmember
material spectrum than are previously reported spectra for
warm and cold crystalline samples prepared at ambient. Thus,
the strengthened spectroscopic evidence, along with geologic
evidence, geochemical models and meteorite studies, strongly
suggest that a major portion of the non-ice material on
Europa that is closely associated with the surface
disruption processes is a somewhat disordered hydrated
salt-like material that is endogenic in origin. This work is
supported by NASA Galileo Mission and JSDAP Program and the
Dept. of Energy Basic Energy Sciences Program.

The author(s) of this abstract have provided an email address
for comments about the abstract:
tom@pgd.hawaii.edu